This invention relates generally to the simulation of impedance using active circuits and in particular to an impedance synthesizer capable of synthesizing a wide range of precise resistance, capacitance, and inductance values.
Calibrating electronic test and measurement equipment is commonly done by measuring a wide range of known impedance values with the equipment to be calibrated and adjusting the circuits in such equipment to precisely match the measured values. The known impedance values are provided by a variety of discrete reference components with known resistance, capacitance, and inductance values that are used as reference standards. Impedance is related to resistance, inductance, and capacitance as a function of frequency in the well known and accepted manner. During a calibration sequence, each reference component is individually measured by the instrument under calibration and the measured value is compared with the known value. Different instruments require different reference components. The result is a calibration method that is cumbersome because each discrete component must be handled separately, relatively inflexible because the number of component values on hand is limited and may not meet the needs of different calibration tasks, and expensive since reference components must be separately characterized and maintained.